About Us Process of Fracking The Marcellus shale is a rock formation that lies more than a mile beneath the earth’s surface. The formation is special because it contains a significant volume of natural gas trapped inside tiny spaces within the rock. It is estimated that the gas within the rock could supply the United States for the next decade – this is a result of the newer technologies used to drill below the earth’s surface. The term “fracking” is a one that you probably have heard. Whether it is on the local news channel, online in an article, or in the newspaper – the word is closely associated with the Marcellus shale drilling. But what exactly is fracking? “Fracking” – or hydraulic fracturing is the process in which oil and gas companies drill into the ground to extract natural gas from the shale rock that lays thousands of feet under the ground. Extracting the gas involves drilling down to the depth of the formation using new horizontal drilling technology that exposes more of the shale. Once the formation is reached, gallons of water, sand, and an extensive list of manmade chemicals are injected into the well under high pressure. This combination inserted in the well, will fracture the rock and release gas. The fracking process is very technical and very intensive.

Through the drilling process, each well can require up to 6 million gallons of water to reach desired completion. Drilling companies typically pipe the water they use from nearby rivers and streams. Below is a step by step process of fracking and the steps it takes to extract natural gas from Marcellus Shale. STEP ONE: Once a drilling location is established, the drilling can begin. A drill bit is then mounted on the end of a drill pipe. As the bit continues to grind its way down, air is pumped down the pipe to flush rock cuttings from the hole and lift them to the surface. The hole is drilled to just underneath the first amount of fresh water underneath the surface. Then the drill pipe and bit are now removed. Next, surface casing is inserted into the hole to isolate the fresh water zone. And, also serves as a foundation for the blowout preventer – a safety device that connects the rig to the wellbore. Then, cement is pumped through the casing and out through the opening of the shoe at the bottom of the casing. The cement is then forced up between the casing and the hole sealing off the wellbore from the fresh water. The cementing process prevents any contamination of the fresh water aquifers.

The pipe and bit are lowered back down the hole to drill through the plug and the cement and continue the vertical section of the well to approximately 500 feet above the plant horizontal leg. This depth is called the kick off point – where the curve will begin so that the horizontal section can be drilled. Again, the pipe and bit are pulled out of the hole. A down hole drilling motor is inserted in the hole to begin horizontal drilling. Horizontal drilling is the most efficient type of drilling technique. Horizontal drilling begins as a typical vertical well, but when the desired distance is reached, it makes a 90 degree turn so that the well can run along the length of the seam. The distance is under a quarter of the mile. It takes over 350 pieces of pipe to drill a 10,500 foot well. While drilling, the drill and drill bit usually require maintenance. This maintenance is also referred to as “tripping pipe.” When target distance is reached, the drill and pipe are removed once again. Production casing is inserted into the full length of the wellbore.

Cement is pumped down the casing and out through the hole, forcing the cement up between the casing and the wall of the hole, filling the open space. Casing the well is a very important process because it permantaly secures the wellbore and it prevents hydrocarbons from seeping out as they are brought to the surface. At this point, the drilling rig is no longer needed and a temporary well head is installed. Hydraulic Fracturing- Shale Natural Gas Extraction - YouTube Hydraulic Fracturing- Shale Natural Gas Extraction Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. The interactive transcript could not be loaded. Loading... Rating is available when the video has been rented. This feature is not available right now. Please try again later. Uploaded on May 17, 2011 This is an educational video describing the unique process of Hydraulic Fracturing used by the oil and gas industry today. Hydraulic Fracturing is a method used to extract natural gas trapped inside shale deposits stored deep underground using controlled explosives and high pressured liquid to create fractures allowing for the flow of natural gas to be pumped to the surface and processed.

Category Shale oil extraction - OilfieldWiki Shale oil extraction Shell's experimental in situ shale oil facility, Piceance Basin , Colorado, United States Process type Shale oil extraction is an industrial process for unconventional oil production. This process converts kerogen in oil shale into shale oil by pyrolysis , hydrogenation , or thermal dissolution . The resultant shale oil is used as fuel oil or upgraded to meet refinery feedstock specifications by adding hydrogen and removing sulfur and nitrogen impurities. Shale oil extraction is usually performed above ground (ex situ processing) by mining the oil shale and then treating it in processing facilities . Other modern technologies perform the processing underground (on-site or in situ processing) by applying heat and extracting the oil via oil wells . The earliest description of the process dates to the 10th century. In 1684, Great Britain granted the first formal extraction process patent. Extraction industries and innovations became widespread during the 19th century. The industry shrank in the mid-20th century following the discovery of large reserves of conventional oil , but high petroleum prices at the beginning of the 21st century have led to renewed interest, accompanied by the development and testing of newer technologies.

As of 2010, major long-standing extraction industries are operating in Estonia , Brazil , and China . Its economic viability usually requires a lack of locally available crude oil. National energy security issues have also played a role in its development. Critics of shale oil extraction pose questions about environmental management issues, such as waste disposal, extensive water use, waste water management, and air pollution. Contents Main article: History of the oil shale industry A.C. Kirk 's retort , used in the mid-to-late 19th century, was one of the first vertical oil shale retorts. Its design is typical of retorts used in the end of 19th and beginning of 20th century. [1] In the 10th century, the Arabian physician Masawaih al-Mardini (Mesue the Younger) wrote of his experiments in extracting oil from "some kind of bituminous shale". [2] The first shale oil extraction patent was granted by the British Crown in 1684 to three people who had "found a way to extract and make great quantities of pitch, tarr, and oyle out of a sort of stone".

[1] [3] [4] Modern industrial extraction of shale oil originated in France with the implementation of a process invented by Alexander Selligue in 1838, improved upon a decade later in Scotland using a process invented by James Young . [1] [5] During the late 19th century, plants were built in Australia, Brazil, Canada, and the United States. [6] The 1894 invention of the Pumpherston retort , which was much less reliant on coal heat than its predecessors, marked the separation of the oil shale industry from the coal industry. [1] China ( Manchuria ), Estonia, New Zealand , South Africa , Spain , Sweden , and Switzerland began extracting shale oil in the early 20th century. However, crude oil discoveries in Texas during the 1920s and in the Middle East in the mid 20th century brought most oil shale industries to a halt. [6] [7] [8] [9] In 1944, the US recommenced shale oil extraction as part of its Synthetic Liquid Fuels Program . These industries continued until oil prices fell sharply in the 1980s.

[7] [10] [11] The last oil shale retort in the US, operated by Unocal Corporation , closed in 1991. [10] [11] The US program was restarted in 2003, followed by a commercial leasing program in 2005 permitting the extraction of oil shale and oil sands on federal lands in accordance with the Energy Policy Act of 2005 . [12] As of 2010 [update] , shale oil extraction is in operation in Estonia, Brazil, and China. [13] [14] [15] Their industries produced about 1,165 million liters (7.33 million barrels ) of shale oil during 2008. [16] Australia, the US, and Canada have tested shale oil extraction techniques via demonstration projects and are planning commercial implementation; Morocco and Jordan have announced their intent to do the same. [6] [10] [15] [17] [18] [19] Only four processes are in commercial use: Kiviter , Galoter , Fushun , and Petrosix .

[14] Processing principles Overview of shale oil extraction Shale oil extraction process decomposes oil shale and converts its kerogen into shale oil—a petroleum -like synthetic crude oil. The process is conducted by pyrolysis , hydrogenation , or thermal dissolution . [20] [21] The efficiencies of extraction processes are often evaluated by comparing their yields to the results of a Fischer Assay performed on a sample of the shale. [22] The oldest and the most common extraction method involves pyrolysis (also known as retorting or destructive distillation ). In this process, oil shale is heated in the absence of oxygen until its kerogen decomposes into condensable shale oil vapors and non-condensable combustible oil shale gas . Oil vapors and oil shale gas are then collected and cooled, causing the shale oil to condense . In addition, oil shale processing produces spent oil shale, which is a solid residue. Spent shale consists of inorganic compounds ( minerals ) and char (some authors use the terms coke residue or semi-coke instead of char)—a carbonaceous residue formed from kerogen. Burning the char off the spent shale produces oil shale ash.

Spent shale and shale ash can be used as ingredients in cement or brick manufacture. [20] [23] The composition of the oil shale may lend added value to the extraction process through the recovery of by-products, including ammonia , sulfur , aromatic compounds , pitch , asphalt , and waxes . [11] Heating the oil shale to pyrolysis temperature and completing the endothermic kerogen decomposition reactions require a source of energy. Some technologies burn other fossil fuels such as natural gas, oil, or coal to generate this heat and experimental methods have used electricity, radio waves , microwaves , or reactive fluids for this purpose. [24] Two strategies are used to reduce, and even eliminate, external heat energy requirements: the oil shale gas and char by-products generated by pyrolysis may be burned as a source of energy, and the heat contained in hot spent oil shale and oil shale ash may be used to pre-heat the raw oil shale. [20] For ex situ processing, oil shale is crushed into smaller pieces, increasing surface area for better extraction. The temperature at which decomposition of oil shale occurs depends on the time-scale of the process.

In ex situ retorting processes, it begins at 300 °C (570 °F) and proceeds more rapidly and completely at higher temperatures. The amount of oil produced is the highest when the temperature ranges between 480 and 520 °C (900 and 970 °F). The ratio of oil shale gas to shale oil generally increases along with retorting temperatures. [20] For a modern in situ process, which might take several months of heating, decomposition may be conducted at temperatures as low as 250 °C (480 °F). Temperatures below 600 °C (1,110 °F) are preferable, as this prevents the decomposition of lime stone and dolomite in the rock and thereby limits carbon dioxide emissions and energy consumption. [25] Hydrogenation and thermal dissolution (reactive fluid processes) extract the oil using hydrogen donors , solvents , or a combination of these. Thermal dissolution involves the application of solvents at elevated temperatures and pressures, increasing oil output by cracking the dissolved organic matter. Different methods produce shale oil with different properties.

[21] [26] [27] [28] Classification of extraction technologies Industry analysts have created several classifications of the technologies used to extract shale oil from oil shale. By process principles: Based on the treatment of raw oil shale by heat and solvents the methods are classified as pyrolysis, hydrogenation, or thermal dissolution. [21] By location: A frequently used distinction considers whether processing is done above or below ground, and classifies the technologies broadly as ex situ (displaced) or in situ (in place). In ex situ processing, also known as above-ground retorting , the oil shale is mined either underground or at the surface and then transported to a processing facility. In contrast, in situ processing converts the kerogen while it is still in the form of an oil shale deposit, following which it is then extracted via oil wells , where it rises in the same way as conventional crude oil. [24] Unlike ex situ processing, it does not involve mining or spent oil shale disposal aboveground as spent oil shale stays underground. [29] By heating method: The method of transfering heat from combustion products to the oil shale may be classified as direct or indirect.

While methods that allow combustion products to contact the oil shale within the retort are classified as direct, methods that burn materials external to the retort to heat another material that contacts the oil shale are described as indirect [14] By heat carrier: Based on the material used to deliver heat energy to the oil shale, processing technologies have been classified into gas heat carrier, solid heat carrier, wall conduction, reactive fluid, and volumetric heating methods. [9] [22] [24] [30] Heat carrier methods can be sub-classified as direct or indirect. The following table shows extraction technologies classified by heating method, heat carrier and location (in situ or ex situ). Classification of processing technologies by heating method and location (according to Alan Burnham) [9] [22] [24] [30] Heating Method – Radio wave, microwave, and electric current processes By raw oil shale particle size: The various ex situ processing technologies may be differentiated by the size of the oil shale particles that are fed into the retorts.

As a rule, gas heat carrier technologies process oil shale lumps varying in diameter from 10 to 100 millimeters (0.4 to 3.9 in), while solid heat carrier and wall conduction technologies process fines which are particles less than 10 millimeters (0.4 in) in diameter. [14] By retort orientation: "Ex-situ" technologies are sometimes classified as vertical or horizontal. Vertical retorts are usually shaft kilns where a bed of shale moves from top to bottom by gravity. Horizontal retorts are usually horizontal rotating drums or screws where shale moves from one end to the other. As a general rule, vertical retorts process lumps using a gas heat carrier, while horizontal retorts process fines using solid heat carrier. By complexity of technology: In situ technologies are usually classified either as true in situ processes or modified in situ processes. True in situ processes do not involve mining or crushing the oil shale. Modified in situ processes involve drilling and fracturing the target oil shale deposit to create voids in the deposit. The voids enable a better flow of gases and fluids through the deposit, thereby increasing the volume and quality of the shale oil produced.

[11] Ex situ technologies Internal combustion Internal combustion technologies burn materials (typically char and oil shale gas) within a vertical shaft retort to supply heat for pyrolysis. [9] [24] Typically raw oil shale particles between 12 millimetres (0.5 in) and 75 millimetres (3.0 in) in size are fed into the top of the retort and are heated by the rising hot gases, which pass through the descending oil shale, thereby causing decomposition of the kerogen at about 500 °C (932 °F) . Shale oil mist, evolved gases and cooled combustion gases are removed from the top of the retort then moved to separation equipment. Condensed shale oil is collected, while non-condensable gas is recycled and used to carry heat up the retort. In the lower part of the retort, air is injected for the combustion which heats the spent oil shale and gases to between 700 °C (1,292 °F) and 900 °C (1,650 °F). Cold recycled gas may enter the bottom of the retort to cool the shale ash.

[9] [20] [31] The Union A and Superior Direct processes depart from this pattern. In the Union A process, oil shale is fed through the bottom of the retort and a pump moves it upward. [9] In the Superior Direct process, oil shale is processed in a horizontal, segmented, doughnut-shaped traveling-grate retort . [9] [25] [32] Internal combustion technologies such as the Paraho Direct are thermally efficient , since combustion of char on the spent shale and heat recovered from the shale ash and evolved gases can provide all the heat requirements of the retort. These technologies can achieve 80-90% of Fischer assay yield. [30] Two well-established shale oil industries use internal combustion technologies: Kiviter process facilities have been operated continuously in Estonia since the 1920s, and a number of Chinese companies operate Fushun process facilities. Common drawbacks of internal combustion technologies are that the combustible oil shale gas is diluted by combustion gases [30] and particles smaller than 10 millimeters (0.4 in) can not be processed.

Uneven distribution of gas across the retort can result in blockages when hot spots cause particles to fuse or disintegrate. Hot recycled solids Hot recycled solids technologies deliver heat to the oil shale by recycling hot solid particles—typically oil shale ash. These technologies usually employ rotating kiln or fluidized bed retorts, fed by fine oil shale particles generally having a diameter of less than 10 millimeters (0.4 in); some technologies use particles even smaller than 2.5 millimeters (0.10 in). The recycled particles are heated in a separate chamber or vessel to about 800 °C (1,470 °F) and then mixed with the raw oil shale to cause the shale to decompose at about 500 °C (932 °F). Oil vapour and shale oil gas are separated from the solids and cooled to condense and collect the oil. Heat recovered from the combustion gases and shale ash may be used to dry and preheat the raw oil shale before it is mixed with the hot recycle solids.

In the Galoter and Enefit processes, the spent oil shale is burnt in a separate furnace and the resulting hot ash is separated from the combustion gas and mixed with oil shale particles in a rotating kiln. Combustion gases from the furnace are used to dry the oil shale in a dryer before mixing with hot ash. [33] The TOSCO II process uses ceramic balls instead of shale ash as the hot recycled solids. [11] The distinguishing feature of the Alberta Taciuk Process (ATP) is that the entire process occurs in a single rotating multi–chamber horizontal vessel. [11] [14] Because the hot recycle solids are heated in a separate furnace, the oil shale gas from these technologies is not diluted with combustion exhaust gas. [9] [24] Another advantage is that there is no limit on the smallest particles that the retort can process, thus allowing all the crushed feed to be used. One disadvantge is that more water is used to handle the resulting finer shale ash. Alberta Taciuk Processor retort Conduction through a wall These technologies transfer heat to the oil shale by conducting it through the retort wall. The shale feed usually consists of fine particles.

Their advantage lies in the fact that retort vapors are not combined with combustion exhaust. [9] [24] The Combustion Resources process uses a hydrogen–fired rotating kiln, where hot gas is circulated through an outer annulus . [34] [35] The Oil-Tech staged electrically heated retort consists of individual inter-connected heating chambers, stacked atop each other. [10] [32] Its principal advantage lies in its modular design , which enhances its portability and adaptability. [32] The Red Leaf Resources EcoShale In-Capsule Process combines surface mining with a lower-temperature heating method similar to in situ processes by operating within the confines of an earthen structure. A hot gas circulated through parallel pipes heats the oil shale rubble. [10] [36] [37] An installation within the empty space created by mining would permit rapid reclamation of the topography. [37] A general drawback of conduction through a wall technologies is that the retorts are more costly when scaled-up due to the resulting large amount of heat conducting walls made of high-temperature alloys.

Externally generated hot gas In general, externally generated hot gas technologies are similar to internal combustion technologies in that they also process oil shale lumps in vertical shaft kilns. Significantly, though, the heat in these technologies is delivered by gases heated outside the retort vessel, and therefore the retort vapors are not diluted with combustion exhaust. [9] [24] The Petrosix and Paraho Indirect employ this technology. [11] [38] In addition to not accepting fine particles as feed, these technologies do not utilize the potential heat of combusting the char on the spent shale and thus must burn more valuable fuels. However, due to the lack of combustion of the spent shale, the oil shale does not exceed 500 °C (932 °F) and significant carbonate mineral decomposition and subsequent CO2 generation can be avoided for some oil shales. Also, these technologies tend to be the more stable and easier to control than internal combustion or hot solid recyle technologies. Reactive fluids Kerogen is tightly bound to the shale and resists dissolution by most solvents . [39] Despite this constraint, extraction using especially reactive fluids has been tested, including those in a supercritical state.

[39] Reactive fluid technologies are suitable for processing oil shales with a low hydrogen content. In these technologies, hydrogen gas (H2) or hydrogen donors (chemicals that donate hydrogen during chemical reactions) react with coke precursors (chemical structures in the oil shale that are prone to form char during retorting but have not yet done so). [40] Reactive fluid technologies include the IGT Hytort (high-pressure H2) process, donor solvent processes, and the Chattanooga fluidized bed reactor . [10] [24] In the IGT Hytort oil shale is processed in a high-pressure hydrogen environment. [41] The Chattanooga process uses a fluidized bed reactor and an associated hydrogen-fired heater for oil shale thermal cracking and hydrogenation. [10] Laboratory results indicate that these technologies can often obtain significantly higher oil yields than pyrolysis processes. Drawbacks are the additional cost and complexity of hydrogen production and high-pressure retort vessels. In situ technologies In situ technologies heat oil shale underground by injecting hot fluids into the rock formation, or by using linear or planar heating sources followed by thermal conduction and convection to distribute heat through the target area.

Shale oil is then recovered through vertical wells drilled into the formation. [10] These technologies are potentially able to extract more shale oil from a given area of land than conventional ex situ processing technologies, as the wells can reach greater depths than surface mines. They present an opportunity to recover shale oil from low-grade deposits that traditional mining techniques could not extract. [42] During World War II a modified in situ extraction process was implemented without significant success in Germany. [9] One of the earliest successful in situ processes was underground gasification by electrical energy ( Ljungström method)—a process exploited between 1940 and 1966 for shale oil extraction at Kvarntorp in Sweden. [9] [43] Prior to the 1980s, many variations of the in situ process were explored in the United States. The first modified in situ oil shale experiment in the United States was conducted by Occidental Petroleum in 1972 at Logan Wash, Colorado. [11] The newest technologies explore a variety of heat sources and heat delivery systems.

Shell 's freeze wall for in situ shale oil production was designed to separate the process from its surroundings Wall conduction Wall conduction in situ technologies use heating elements or heating pipes placed within the oil shale formation. The Shell in situ conversion process (Shell ICP) uses electrical heating elements for heating the oil shale layer to between 650 and 700 °F (340 and 370 °C) over a period of approximately four years. [44] The processing area is isolated from surrounding groundwater by a freeze wall consisting of wells filled with a circulating super-chilled fluid. [22] [29] Disadvantages of this process are large electrical power consumption, extensive water use, and the risk of groundwater pollution. [45] The process, under development since the early 1980s, is tested at the Mahogany test site in the Piceance Basin . 1,700 barrels (270 m3) of oil were extracted in 2004 at a 30-by-40-foot (9.1 by 12 m) testing area.

[29] [44] [46] American Shale Oil CCR Process In the American Shale Oil CCR Process, superheated steam or another heat transfer medium is circulated through a series of pipes placed below the oil shale layer to be extracted. The system combines horizontal wells, through which steam is passed, and vertical wells, which provide both vertical heat transfer through refluxing of converted shale oil and a means to collect the produced hydrocarbons. Heat is supplied by combustion of natural gas or propane in the initial phase and by oil shale gas at a later stage. [10] [47] The Independent Energy Partners ' Geothermic Fuels Cells Process (IEP GFC) extracts shale oil by exploiting a high-temperature stack of fuel cells . The cells, placed in the oil shale formation, are fueled by natural gas during a warm-up period and afterward by oil shale gas generated by its own waste heat. [10] [43] Externally generated hot gas Chevron CRUSH process Externally generated hot gas in situ technologies use hot gases that are heated above-ground and then injected into the oil shale formation.

The Chevron CRUSH process, developed by Chevron Corporation in partnership with Los Alamos National Laboratory , injects heated carbon dioxide into the formation via drilled wells and heats the formation through a series of horizontal fractures in which the gas circulates. [48] General Synfuels International has proposed the Omnishale process which involves injecting super-heated air into the oil shale formation. [10] [37] Mountain West Energy 's In Situ Vapor Extraction process uses similar principles of injection of high-temperature gas. [10] [49] ExxonMobil Electrofrac Main article: ExxonMobil Electrofrac ExxonMobil 's in situ technology ( ExxonMobil Electrofrac ) uses electrical heating with elements of both wall conduction and volumetric heating methods. It injects an electrically conductive material such as calcined petroleum coke into the hydraulic fractures created in the oil shale formation which then forms a heating element. [10] [50] [51] Heating wells are placed in a parallel row with a second horizontal well intersecting them at their toe. This allows opposing electrical charges to be applied at either end.

[10] [51] Volumetric heating Artist's rendition of a radio wave-based extraction facility The Illinois Institute of Technology developed the concept of oil shale volumetric heating using radio waves (radio frequency processing) during the late 1970s. This technology was further developed by Lawrence Livermore National Laboratory . The oil shale would be heated by vertical electrode arrays . Deeper volumes could be processed at slower heating rates by installations spaced at tens of meters. The concept presumes a radio frequency at which the skin depth is many tens of meters, thereby overcoming the thermal diffusion times needed for conductive heating. [24] [52] [53] Its drawbacks include intensive electrical demand and the possibility that groundwater or char would absorb undue amounts of the energy. [24] Radio frequency processing in conjunction with critical fluids is being developed by Raytheon together with CF Technologies and tested by Schlumberger . [54] [55] Microwave heating technologies are based on the same principles as radio wave heating, although it is believed that radio wave heating is an improvement over microwave heating because its energy can penetrate farther into the oil shale formation. [56] The microwave heating process is being tested by Global Resource Corporation .

[57] Electro-Petroleum proposes electrically enhanced oil recovery by the passage of direct current between cathodes in producing wells and anodes located either at the surface or at depth in other wells. The passage of the current through the oil shale formation results in resistive Joule heating . [10] Economics Main article: Oil shale economics The dominant question for shale oil production is under what conditions shale oil is economically viable. The various attempts to develop oil shale deposits have succeeded only when the shale-oil production cost in a given region is lower than the price of petroleum or its other substitutes. According to a survey conducted by the RAND Corporation , the cost of producing shale oil at a hypothetical surface retorting complex in the United States (comprising a mine, retorting plant, upgrading plant , supporting utilities, and spent oil shale reclamation), would be in a range of US$ 70–95 per barrel ($440–600/m3), adjusted to 2005 values.

Assuming a gradual increase in output after the start of commercial production, the analysis projects a gradual reduction in processing costs to $30–40 per barrel ($190–250/m3) after achieving the milestone of 1 billion barrels (160×10 ^ 6 m3). [8] [29] Royal Dutch Shell has announced that its Shell ICP technology would realize a profit when crude oil prices are higher than $30 per barrel ($190/m3), while some technologies at full-scale production assert profitability at oil prices even lower than $20 per barrel ($130/m3). [11] [58] To increase the efficiency of oil shale retorting and by this the viability of the shale oil production, researchers have proposed and tested several co-pyrolysis processes, in which other materials such as biomass , peat , waste bitumen , or rubber and plastic wastes are retorted along with the oil shale.

[59] [60] [61] [62] [63] Some modified technologies propose combining a fluidized bed retort with a circulated fluidized bed furnace for burning the by-products of pyrolysis (char and oil shale gas) and thereby improving oil yield, increasing throughput, and decreasing retorting time. [64] Other ways of improving the economics of shale oil extraction are to increase the size of the operation to achieve economies of scale , use oil shale that is a by-product of coal mining such as at Fushun China, produce specialty chemicals as by Viru Keemia Grupp in Estonia, co-generate electricity from the waste heat and process high grade oil shale that yields more oil per shale processed. A possible measure of the viability of oil shale as an energy source lies in the ratio of the energy in the extracted oil to the energy used in its mining and processing (Energy Returned on Energy Invested, or EROEI ). A 1984 study estimated the EROEI of the various known oil shale deposits as varying between 0.7–13.3; [65] Some companies and newer technologies assert an EROEI between 3 and 10.

To increase the EROEI, several combined technologies were proposed. These include the usage of process waste heat, e.g. gasification or combustion of the residual carbon (char), and the usage of waste heat from other industrial processes, such as coal gasification and nuclear power generation. [10] [66] [67] The water requirements of extraction processes are an additional economic consideration in regions where water is a scarce resource. Environmental considerations Main article: Environmental impact of the oil shale industry Objections to its potential environmental impact have stalled governmental support for extraction of shale oil in some countries, such as Australia. [68] Shale oil extraction may involve a number of different environmental impacts that vary with process technologies. Depending on the geological conditions and mining techniques, mining impacts may include acid drainage induced by the sudden rapid exposure and subsequent oxidation of formerly buried materials, the introduction of metals into surface water and groundwater, increased erosion , sulfur gas emissions, and air pollution caused by the production of particulates during processing, transport, and support activities. [52] [69] Surface mining for ex situ processing, as with in situ processing, requires extensive land use and ex situ thermal processing generates wastes that require disposal.

Mining, processing, spent oil shale disposal, and waste treatment require land to be withdrawn from traditional uses. [8] [70] Depending on the processing technology, the waste material may contain pollutants including sulfates , heavy metals , and polycyclic aromatic hydrocarbons , some of which are toxic and carcinogenic . [71] [72] Experimental in situ conversion processes may reduce some of these impacts, but may instead cause other problems, such as groundwater pollution. Spent shale often presents a disposal problem The production and usage of oil shale usually generates more greenhouse gas emissions, including carbon dioxide, than conventional fossil fuels. [70] Depending on the technology and the oil shale composition, shale oil extraction processes may also emit sulfur dioxide , hydrogen sulfide , carbonyl sulfide , and nitrogen oxides . [73] Developing carbon capture and storage technologies may reduce the processes' carbon footprint. [74] Concerns have been raised over the oil shale industry's use of water, particularly in arid regions where water consumption is a sensitive issue. [75] Above-ground retorting typically consumes between one and five barrels of water per barrel of produced shale oil, depending on technology.

[29] [76] Water is usually used for spent oil shale cooling and oil shale ash disposal. In situ processing, according to one estimate, uses about one-tenth as much water. [77] In other areas, water must be pumped out of oil shale mines. The resulting fall in the water table may have negative effects on nearby arable land and forests. [8] A 2008 programmatic environmental impact statement issued by the United States Bureau of Land Management stated that surface mining and retort operations produce 2 to 10 U.S. gallons (7.6 to 38 l ; 1.7 to 8.3 imp gal ) of waste water per 1 short ton (0.91 t ) of processed oil shale. [76] See also Script error ↑ The Process of Shale Gas Development - Shale Gas : Shale Gas External Sources The Process of Shale Gas Development Europe is still in the early phases of horizontally drilling and fracturing wells to extract shale gas, however the process of hydraulic fracturing has been used in Europe for decades as an industrial process to stimulate conventional oil and gas wells, water wells and geothermal wells.

In Germany, more than 300 conventional wells have been stimulated using this technique. Around 200 onshore oil and gas wells in the UK have been stimulated by hydraulic fracturing. In the United States, hydraulic fracturing was combined with horizontal drilling during the 1980s and 1990s and enabled natural gas trapped in shale rock to be commercially extracted. This has led the US to become the leading oil and gas producer in the world, where horizontal wells have rapidly outstripped the use of vertical wells. This section provides further information on the process employed to extract natural gas from shale rock. The drilling phase of a shale gas well is the same process as for conventional wells. Hydraulic Fracturing Hydraulic fracturing is the process most commonly used to release natural gas and oil from deep beneath the surface of the earth. Though it has only recently come to the attention of the general public, hydraulic fracturing is a mature technology, first used in the 1940s in the US to stimulate oil and gas wells and increase production rates. In Europe, hydraulic fracturing has been used since the 1960s, for conventional oil and gas production and for the recovery of geothermal energy.

Hydraulic fracturing is particularly important in the context of shale gas development. As shale gas reservoirs are trapped within rock formations of very low permeability, the gas can only be released into the well by stimulating the shale formation through hydraulic fracturing. Combined with horizontal drilling it maximises extraction by allowing multiple fractures along the shale bed which in turn allows the gas to be commercially extracted. Developing shale gas: a step-by-step guide An appropriate site is prepared and a wellbore is drilled to a length thousands of metres below the surface. A horizontal section will then be drilled through the target shale layer. Stages of small perforations are created at the very bottom of the wellbore. Water and sand is mixed with a small quantity of additives and pumped at high pressure, several hundreds of metres down the wellbore. The fracturing solution is pumped into the shale formation, creating fissures and opening existing fissure in the rock. The sand in the fracturing fluid then remains in the cracks created, keeping them open. This process creates passageways through which the natural gas, previously trapped in the shale rock, can now flow.

During the fracturing process, companies monitor in real-time the rock response and well pressure, enabling them to ensure the safety of operations. Hydraulic fracturing operations take place for 3-10 days where water is pumped under high pressure to complete the well. Depending on the specific shale formation, it will take between three and ten days to complete the hydraulic fracturing process. Once the water flowing up the wellbore is collected, the well is prepared to produce a steady stream of natural gas for decades to come. After the well is complete, the surface level will be restored to its original state. Throughout the process, good practice well construction techniques seek to mitigate any risk of chemical additives leaking into surrounding surface water, groundwater, land or air. Well Casing While hydraulic fracturing typically takes place one to three kilometres below the surface, drilling for shale gas can (but not always) penetrate the water table. The proper casing of shale gas wells is vital for the safety of operations.

Good practice well construction techniques employ multiple barrier layers of steel and cement to isolate the well from groundwater: Conductor casing: this is installed prior to the arrival of the drilling rig and is there to prevent the top section of the well from collapsing Surface casing: going up to 500m underground, the surface casing helps to stabilise the wellbore as well as to protect groundwater deposits from being contaminated by any potential gas leakage Intermediate casing: placed between the surface and production cases, it ensures that there can be no leakage path from the shale reservoir up to the aquifer. The cement layer protects the casing from corrosion and provides zonal isolation Production casing: the deepest section of casing in a well, it provides the path from the surface of the well to the gas-producing shale formation This layered design ensures that even if one of the casings would rupture, nothing would be able to migrate outside the wellbore. In addition, all wells are pressure-tested to guarantee integrity before hydraulic fracturing takes place. Chemical additives The International Oil and Gas Producers Association (IOGP) states that hydraulic fracturing fluids are composed mostly of water and sand (99.5%).

On average, chemical additives make up around only 0.5% of a fracturing solution. A typical fracturing treatment will use around twelve chemical additives at these low concentrations, depending on the characteristics of the water and of the shale formation to be fractured. These chemicals fulfil a specific purpose, from helping to preserve well integrity to reducing onsite emissions. A list of the chemical additives used in the US is available though the FracFocus website or NGS Facts in Europe. NGS Facts All the chemical additives used in fracturing solutions in Europe fully comply with European and national regulations. Furthermore, the industry supports full disclosure of these chemicals to the appropriate regulatory authorities and is committed to keeping the public updated about the chemical additives used in local fracturing operations. For this purpose IOGP has set up NGSFacts.org. This website mirrors the approach taken by the U.S. Ground Water Protection Council and U.S. Department of Energy in setting up FracFocus. Like FracFocus, NGS Facts allows the general public to search for specific information on the compounds used in the hydraulic fracturing of individual local wells.

Whilst shale gas development is still in its infancy in the EU, the NGS Facts database has been designed to expand as operations become increasingly widespread in Europe, as has been seen with Frac Focus in the US. Currently Frac Focus holds details of more than 47,000 individual well sites, with this number growing by several hundred each month. What is Fracking? What Is Fracking? States What is Fracking? Learn how fracking uses water to extract oil and natural gas from shale plays, why fracking is an economic and energy security solution, and where fracking is safely taking place in America.

Question: Which process is used to extract shale gas from the ground?
Answer: Fracking